X-ray radiography and tomography are important methods for a variety of applications, for example non-destructive investigation of bulk samples, quality inspection of industrial products and non-invasive examination of anatomical structures and tissue regions of interest in the interior of a patient's body.
X-ray imaging based on attenuation of x-rays may yield excellent results where highly absorbing anatomical structures such as bones are embedded in a tissue of relatively weakly absorbing material. This is due to the fact that the penetration depth of hard x-ray beams may be rather high, which allows for recording sharp projections of the attenuation coefficient.
In US2009/0304149 A1 and US2011/0216878 A1 x-ray imaging system adapted for detecting attenuation based image data are shown.
When different kinds of tissue with similar absorption cross-sections are under examination (for example in mammography or angiography), the contrast of x-ray absorption may be relatively poor. In this case, phase contrast x-ray radiography and tomography may be employed, where the change of phase of the x-rays penetrating the object of interest is examined.
There are several methods to retrieve phase information. Currently, the most popular is a Talbot interferometer type method, which may be grating based. However, there are alternatives, among which the in-line holography approach is appealing because it may not require any optical instruments like monochromators or gratings which need to be aligned carefully.
In WO 2008/006470 A1 an x-ray interferometer for phase contrast imaging is shown.